The invention relates to a parking brake system for vehicles, in particular passenger cars, having a power-assistance-generating actuator unit for pulling on or releasing at least one control cable for a braking device of the vehicle, having an electronic control device whose output variable is used to activate the actuator unit, the control device being supplied with input variables, in particular from an operator device, from sensors and/or switches or the like, and it being possible to change the output variable as a function of the input variable.